Intravoxel incoherent motion model&ndash;based analysis of diffusion-weighted magnetic resonance imaging with 3 <em>b</em>-values for response assessment in locoregional therapy of hepatocellular carcinoma

Abstract

PurposeThe aim of this study was to evaluate an intravoxel incoherent motion (IVIM) model–based analysis of diffusion-weighted imaging (DWI) for assessing the response of hepatocellular carcinoma (HCC) to locoregional therapy.Patients and methodsRespiratory-gated DWI (b=0, 50, and 800 s/mm2) was retrospectively analyzed in 25 patients who underwent magnetic resonance imaging at 1.5 T before and 6 weeks following the first cycle of transarterial chemoembolization therapy, transarterial ethanol-lipiodol embolization therapy, and transarterial radioembolization therapy. In addition to the determination of apparent diffusion coefficient, ADC(0,800), an estimation of the diffusion coefficient, D′, and the perfusion fraction, f′, was performed by using a simplified IVIM approach. Parameters were analyzed voxel-wise. Tumor response was assessed in a central slice by using a region of interest (ROI) covering the whole tumor. HCCs were categorized into two groups, responders and nonresponders, according to tumor size changes on first and second follow ups (if available) and changes of contrast-enhanced region on the first follow up.ResultsIn total, 31 HCCs were analyzed: 17 lesions were assigned to responders and 14 were to nonresponders. In responders, ADC(0,800) and D′ were increased after therapy by ~30% (P=0.00004) and ~42% (P=0.00001), respectively, whereas f′ was decreased by ~37% (P=0.00094). No significant changes were found in nonresponders. Responders and nonresponders were better differentiated by changes in D′ than by changes in ADC(0,800) (area under the curve =0.878 vs 0.819 or 0.714, respectively).ConclusionIn patients with HCCs undergoing embolization therapy, diffusion changes were better reflected by D′ than by conventional ADC(0,800), which is influenced by counteracting perfusion changes as assessed by f′.

Comparison of methods for estimation of the intravoxel incoherent motion (IVIM) diffusion coefficient (D) and perfusion fraction (f)

“…This is in line with previous findings regarding tumor tissue characterization and therapy-response assessment [8,13], although contradicting results have been reported for prostate cancer [16]. The distribution of D and f was substantially altered by the treatments, suggesting a therapeutic effect on at least a subset of the studied tumors.…”

“…has not yet been established and thus varies between studies [12,13], although some work has been done regarding optimization of three-b-value protocols [27,28]. However, as long as the chosen model is valid for the particular b values, choice of b values should only have minor effects on the observed estimation trends.…”

“…Therefore, estimating only D and f has been employed in several recent studies [12][13][14]. This still enables extraction of both diffusion (D) and perfusion (f) information while reducing the demands on image quality in terms of signal-to-noise ratio (SNR).…”

Diffusion-weighted Whole-body MRI at 3 Tesla for the Detection and Discrimination of Pulmonary Tumors

“…In the presented 3.0 T study, in addition to b-values of 0 and 1000 s/mm2, a low b-value of 50s/mm 2 was included in the sequence for a rough assessment of perfusion effects. From the used three b-values it is possible to obtain perfusion sensitive biomarkers as ADC(0, 50) [34] , estimation of perfusion fraction [35][36][37][38][39][40] or simply the ADC Diffusion-Weighted Whole-Body MRI difference between the conventionally used ADC(0,1000) and the ADC(50, 1000), which is less affected by perfusion effects, as in the present study. With this simplified IVIM approach, a further separation into perfusion fraction and pseudodiffusion coefficient as obtained for full IVIM approaches is not possible.…”

MRI assessment of hepatocellular carcinoma after locoregional therapy

“…Woo et al [107] and Mürtz et al [108] found a significant correlation between IVIM-derived parameter (fp) and percent of arterial enhancement whether in the initial diagnosis of HCC or after the locoregional therapy. Hence, it could be used after locoregional therapy to distinguish responders from non-responders especially if there is contraindication for contrast administration (Fig.…”